1. Field of the Invention
The present invention relates to a blanking device for blanking multiple charged particle beams and to a multi charged particle beam writing method. More specifically, the present invention relates to a blanking device used in multi-beam writing, and to a writing method using the blanking device, for example.
2. Description of Related Art
The lithography technique that advances miniaturization of semiconductor devices is extremely important as a unique process whereby patterns are formed in semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is decreasing year by year. The electron beam (EB) writing technique, which intrinsically has excellent resolution, is used for writing or “drawing” a pattern on a wafer and the like with electron beams.
As an example employing the electron beam writing technique, a writing apparatus using multiple beams (multi-beams) can be cited. Compared with the case of writing a pattern by using a single electron beam, since it is possible to emit multiple beams at a time in multiple writing, the throughput can be greatly increased. For example, in the writing apparatus employing a multi-beam system, multiple beams are formed by letting an electron beam emitted from an electron gun assembly pass through a mask with a plurality of holes, blanking control is performed for each of the beams, and each unblocked beam is reduced by an optical system and deflected by a deflector so as to irradiate a desired position on a target object or “sample”.
In multi-beam writing, the dose of each beam is individually controlled based on an irradiation time. For highly accurately controlling such a dose of each beam, it is necessary to perform blanking control to provide on or off of a beam at high speed. In a writing apparatus of a multi-beam system, a blanking control circuit for each beam is placed on a blanking plate where each blanker for use in multiple beams is arranged. It has been considered that a shift register is embedded in each control circuit for each beam, and a signal from a pad is input into shift registers connected in series in each row in a plurality of blankers arranged in a matrix.
Here, for transmitting data to N shift registers connected in series, it is necessary to execute clock operations N times by the shift registers. The heating value of a shift register is proportional to the number of times of clock operation per unit time. On the other hand, if the number of beams increases, the number of shift registers arranged in one row increases. Therefore, the number of times of clock operation per unit time increases, and the heating value increases. Consequently, the heating value of a blanking plate increases. Since the blanking plate is arranged in a vacuum region, and, further, the shift register is arranged in a membrane region of the blanking plate, the heat exhaust efficiency is low. Accordingly, for controlling the heating value to be within an acceptable value, limitation occurs to the number of times of clock operation per unit time. Thus, it becomes difficult to perform a high-speed operation. Furthermore, when the number of beams increases and the number of shift registers arranged in one row increases, data transmission will take time. Therefore, also from this point of view, it becomes difficult to achieve a high-speed operation.
Moreover, for inputting a signal from a pad to shift registers connected in series in each row, it is necessary to arrange, on the blanking plate, pads of the same number as that of rows of a plurality of blankers. Therefore, if aiming to reduce the number of shift registers arranged in one row by dividing them, it will be necessary to increase the number of pads. However, since each blanker and each control circuit arranged at the blanking plate are manufactured using the LSI manufacturing technology, there is an upper limit for the chip size, which is about 20 mm. Therefore, if the number of beams increases and thus the number of rows increases, it becomes difficult to arrange pads, whose number is corresponding to the number of the rows, at one side of the blanking plate. For example, assuming that the beam arrangement is 512×512, the beam pitch is about 32 μm and thus the distance between pads becomes too narrow to arrange the pads. Accordingly, it is required to inhibit the increase of the number of pads.
As technology relating to the blanking system using shift registers, there is disclosed technology in which a plurality of blankers (electrodes) are connected in parallel to one circuit where a shift register and a switch are arranged, and a plurality of circuits each have the configuration described above are in order connected to one data line so as to perform data transmission (e.g., refer to Japanese Published Unexamined Patent Application (JP-A) No. 2009-502033). However, though not described in the disclosed technology, since a large number of times of clock operation is still needed even if shift registers in accordance with the number of blankers are arranged in each circuit, it is still difficult to solve the above-described problem that occurs when the number of beams increases and therefore the number of shift registers arranged in one row increases.